The present invention relates to a method of producing an optical waveguide system, an optical device and optical coupler employing the optical waveguide system, an optical network and an optical circuit board.
In one aspect, present invention relates to a method of producing optical waveguide systems. To be more specific, the present invention relates to a method of producing optical waveguide systems, refractive index distributions and optical coupling paths by self-organization. The method of the present invention may be used with advantages for the production of optical waveguide systems, particularly bend waveguides, space beam couplers, Z-axis waveguides, waveguide couplers, LD couplers, branch waveguides, star couplers, cross waveguides, space waveguides, wavelength filters and mode converters.
The fields of data processing and communication have seen dramatic progress in the area of optical wiring and interconnection, and the diffusion of optical technology such as optical parallel processors and "fiber to the home" is expected to continue in the future. This will require various types of optical integrated circuits such as waveguide devices, while it will also be necessary to simplify and render more efficient optical coupling between various optical devices, including fibers.
Although there have been conventionally known methods such as etching as methods of forming waveguides, a disadvantage of this method is the low positioning precision and low degree of freedom of shape.
Nevertheless, the following problems remain.
(1) Although improvement in positioning precision has been attempted by the V-groove method, performance which sufficiently satisfies the demands for high efficiency and high tolerance has not yet been achieved.
(2) The angles of divergence of emitted light from the different optical devices sometimes differ.
(3) The mode sizes of the emitting ends of the different optical devices sometimes differ.
Furthermore, in Japanese Unexamined Patent Publication Nos. 55-43538 and 60-173508, there have been proposed methods of improving optical coupling efficiency by irradiating light from a waveguide on a substance whose refractive index changes with light irradiation, to form a lens-like refractive index distribution or waveguide. However, since these methods do not employ a self-focusing effect, a self-organizing effect of the waveguide itself is not obtained, and therefore the degree of efficiency improvement, safety and the degree of freedom of the device structure is less than sufficient.
The present invention is aimed at solving the above-mentioned problems of the prior art, by realizing a method of producing a waveguide or refractive index distribution which is self-organized using a substance whose optical refractive index changes with light irradiation (hereunder referred to as "photorefractive" or a substance which insolubilizes (cures) as its optical refractive index changes with light irradiation (hereunder referred to as "photosensitive material"), as well as a device which employs the same.
It is an object of the present invention, therefore, to provide a method of automatically burrowing out a waveguide by light incidence and a device formed thereby; a method of forming a waveguide circuit network by automatically combining a few waveguides created by light incidence and a method of producing tapered and other refractive index distributions formed by a self-focusing effect and a device formed thereby; and a self-aligned optical coupler employing a waveguide or refractive index distribution obtained in such a manner.
It is another object of the present invention to overcome the above-mentioned problems (1)-(3) by forming refractive index distributions in photorefractive materials and photosensitive materials by light emission from emitting ends of optical devices, and to provide structures and methods of production which may be applied to various devices and modules.
It will be convenient according to the present invention to refer to these devices and optical couplers collectively as self-organized lightwave networks (SOLNET).
According to the present invention, in order to overcome the above-mentioned problems, there is provided a method of producing an optical waveguide or refractive index distribution which is characterized by irradiating a photorefractive material with light of a wavelength which changes its refractive index, and forming an optical waveguide or refractive index distribution while inducing self-focusing.
There is also provided according to the present invention a method of producing an optical waveguide or refractive index distribution which is characterized by irradiating a photosensitive material with light of a wavelength which changes its refractive index and insolubilizes the material, and forming an optical waveguide or refractive index distribution while inducing self-focusing and insolubilizing the photosensitive material.
There is also provided according to the present invention a self-aligned optical coupling method which is characterized by situating an a photorefractive material in the entirety or part of the area between a plurality of optical devices, irradiating the photorefractive material with light from one or a plurality of optical devices of a wavelength at which its refractive index changes, and using the optical waveguide or refractive index distribution formed while inducing self-focusing, to accomplish optical coupling between the optical devices.
There is also provided according to the present invention a self-aligned optical coupling method which is characterized by situating a photosensitive material in the entirety or part of the area between a plurality of optical devices, irradiating the photosensitive material with light from one or a plurality of optical devices of a wavelength at which its refractive index changes and the material is insolubilized, and using the optical waveguide or refractive index distribution formed while inducing self-focusing and insolubilizing the photosensitive material, to accomplish optical coupling between the optical devices.
There is also provided according to the present invention a method of forming a waveguide, refractive index distribution or optical coupling path as described above using light of a plurality of wavelengths, either with or without self-focusing.
In another aspect, the present invention relates to a non-linear optical material, and an optical circuit device and optical circuit substrate in which it is used.
Optical circuits are predicted to play an important role in the optical interconnections of parallel computers and in various optical systems such as optical switching systems in the future. Non-linear optical devices, and particularly electro-optical (EO) devices, optical waveguide amplifiers and optical waveguide lasers, are indispensable elementary technologies for the function of these optical circuits.
Although LN (LiNbO.sub.3) single crystals and compound semiconductor superlattices were used as EO materials in the past, these materials have problems including a low degree of freedom for the substrate composition, requiring considerable labor for lamination, having a high dielectric constant, not facilitating low power and high-speed driving, being difficult to apply to a large surface area, and being difficult to combine with other devices.
In contrast, since organic polymer materials have the characteristics of a large degree of freedom for substrate composition, easy lamination, low dielectric constant, being suited for low power and high-speed driving, easy application over a large surface area and being able to be easily combined with other devices, they are suitable for increasing the functions and degree of integration of optical circuits. At present, however, there is apprehension concerning the reliability of these materials due to the occurrence of relaxation deterioration.
In addition, we previously proposed a process using an optical power source as a useful optical wiring process (such as in Japanese Patent Application No. 6-5009231). This process consisted of allowing pump light to enter a waveguide optical amplifier and waveguide laser, forming an optical power source, picking up the light by an EO switch and then transmitting optical signals. In this case, since the optical power source itself does not have remarkable EO effects, it was necessary to laminate or insert an EO layer.
In the second aspect of the present invention, it is an object to further improve on the above-mentioned proposed technology and provide a non-linear optical material, optical power source, optical waveguide laser and optical waveguide amplifier that have EO effects, as well as non-linear optical devices, non-linear optical amplifier, optical waveguide laser and optical circuit substrate that use the above, that have a large degree of freedom for the substrate composition, facilitate easy lamination, have a low dielectric constant, are suited to low power and high-speed driving, are easily applied to large surface areas, and can be easily combined with other devices.
In order to solve the above-mentioned problems, the present invention provides a non-linear optical material comprising a multi-layer film that contains an amorphous or polycrystalline inorganic substance; wherein, centro-symmetry in the direction of film thickness is eliminated by laminating different substances, centro-symmetry is eliminated by changing the composition of the same type of substance, changing the type of doping substance and/or amount of doping, or changing layer thickness and/or the amount of doping, or centro-symmetry is eliminated by combining either of the above two methods.
The present invention also provides a non-linear optical material comprising a multi-layer film containing an organic crystal material, an amorphous material, a polycrystalline material or a single crystal material; wherein, centro-symmetry in the direction of film thickness is eliminated by laminating different substances, centro-symmetry is eliminated by changing the composition of the same type of substance, changing the type of doping substance and/or amount of doping, or changing layer thickness and/or the amount of doping, or central symmetry is eliminated by combining either of the above two methods.
The present invention also provides a non-linear optical material wherein rare earth ions or molecules containing rare earth ions are contained in a non-linear optical polymer.
Moreover, the present invention provides a non-linear optical device, non-linear optical amplifier, optical waveguide laser and optical circuit substrate that use the above-mentioned material.
In the above-mentioned first non-linear optical material as claimed in the present invention, the multi-layer film preferably has for its main component a material selected from the group consisting of a-Si:H, a-SiNy, a-SiOx, a-SiCz and a-Ge:H, or a mixed crystal of two or more types of said materials. Alternatively, this multi-layer film may have for its main component a transition metal compound, a glass material, or these materials may contain rare earth ions as desired.
In the above-mentioned second non-linear optical material as claimed in the present invention, the multi-layer film preferably has for its main component an organic polymer, and said organic polymer may contain rare earth ions and/or molecules containing rare earth ions as desired.
In a further aspect, the present invention relates to an opto-electronic device and a method of preparing it. More specifically, the present invention particularly uses an organic conjugated polymer film formed by vapor deposition polymerization as a functional layer of an opto-electronic device. Examples of said opto-electronic device include useful light emitting devices such as a light emitting display, laser and interior lighting, light receiving devices such as a photodiode, as well as solar cells.
EL (electro-luminescent) devices using inorganic materials were known as examples of light emitting devices of the prior art. Although these devices emitted red to blue light by adding Mn or Tb and so forth to ZnS and ZnSe, since the emission efficiency at a driving voltage of 20 V and above was a maximum of roughly only 1%, it was difficult to obtain devices having large surface areas such as displays.
As examples of devices such as LED that use organic materials, high-luminance light emitting devices are known to be able to manufactured by forming an organic monomer film by vapor deposition. However, monomer films have the problems of decreased emission efficiency due to crystallization, inadequate film strength and insufficient durability. In addition, devices able to emit red to blue light are also known to be able to be manufactured by forming an organic polymer film by spin coating or dip coating. In this case, however, there was the problem of solvent remaining in the resulting film since the organic polymer had to be dissolved in solvent during coating. In addition, since the polymer had to be given a soluble portion for solubilization of the polymer, there was also the problem of decreased emission efficiency.
On the other hand, in the case of lasers, photodiodes, solar cells and so forth, it is still difficult to produce these devices at the practical level using organic polymers.
In the third aspect, in order to solve the problems of the prior art as described above, the object of the present invention is to realize a sufficiently practical opto-electronic device by using an organic polymer.
In order to solve the above-mentioned problems, the present invention provides an opto-electronic device containing an organic conjugated polymer film deposited on a substrate by vapor deposition polymerization as at least one functional layer.
Examples of opto-electronic devices obtained by the present invention include useful light emitting devices such as light emitting displays, lasers and interior lighting, light receiving devices such as photodiodes, as well as solar cells.
In a further aspect of the present invention relates to optical networks and optical circuit boards. Particularly, it relates to an optical network and optical circuit board capable of increasing the speed of computers.
The most effective method of speeding up computers is to make them parallel. In order to achieve this, it is important to raise the wiring switching (exchange) efficiency. Conventional electrical exchange has required large switching apparatuses and massive consumption of power, thus frustrating efforts to realize compact systems.
In the fourth aspect, the main object of the present invention, therefore, is to improve this condition by forming a loop-shaped optical waveguide in an optical circuit board for packet exchange.
In order to overcome the above-mentioned problems, the present invention provides an optical network provided with optical wiring for exchanging signals between processing elements selected from electronic elements, electronic apparatuses, electro-optical elements and electro-optical apparatuses, which is characterized in that the optical paths form loops passing near all or some of the processing elements, and there are provided at least one each of an optical transmitter which sends optical signals to all or some of the processing elements and a receiver which converts the optical signals to electrical signals, which are coupled with the optical path loops.